A cooling tower sweeper system is a simple system consisting of a filter, a pump, a range of plastic pipework, and various nozzles that are installed around the perimeter of the tower cold water basin floor. The nozzles are placed to spray water evenly across it at velocity, which moves and cleans the pollutants, debris, and sediment that can build up over time, flushing them to the sweeper outlet. If the debris etc., is not dealt with, it can cause maintenance and efficiency issues for the tower.
Benefits of using a Sweeper System
- Provides side stream filtration and better water conditions.
- Reduces blowdown requirements / water usage / water costs.
- Reduces chemicals usage and costs for cleaning the water in the system.
- Keeps the tower operating longer as no need to shut down regularly for cleaning, lowering costs.
- Minimizes corrosion in the tower and the condenser system.
- Helps maintain system and equipment efficiency, dirty polluted water can affect the operation of the tower an equipment.
- Minimises ‘low water flow’ areas in the basin.
- Reduces the opportunity for biological growth.
- Can integrate with existing water filtration systems.
- Based on the benefits, return on investment is quite quick [see below section]
Cooling Tower Sweeper System Components
The system, as noted above, is made up of the following components:
- Filter / separator
- Sweeper piping [discharge / nozzles]
- Nozzles / sweeper jets
- Sweeper piping [outlet / pump suction pipe]
- Skid / base
The filter is generally a centrifugal chamber that removes the pollutants, debris, and sediment before flowing the clean water back into the basis.
The debris that the filter has collected will accumulate at the bottom of the separator. It will either be manually or automatically, via a time clock, flushed to drain.
Not always will it be a centrifugal filter; disc and sand filters can also be used.
Using a filter can also help reduce the blowdown requirements by removing the contaminants from the water.
A pump is used to create a flow through the system and push the water through the basin nozzles to create the jets required for cleaning.
Supply pipework, usually an array of PVC piping, is installed on the discharge outlet of the pump and connected to the tower and pipework that is supplying the nozzles with water.
A range of pipework, installed in a loop, allows the nozzles to connect to the system.
Nozzles are installed in specific locations across the tower basin to jet water, creating a hydraulic sweep, pushing the pollutants, debris, and sediment across to the ‘sweeper outlet’ where it enters the filtration system before being delivered back into the system.
The disturbance that the nozzles create in the water also helps to minimize biological growth.
Sweeper outlet / suction pipework
In the corner of the basin will be the ‘sweeper outlet,’ where the nozzles will sweep the pollutants, debris, and sediment into.
The outlet is connected to the filtration system before the suction side of the pump.
The controls are straightforward, usually just interlocked with the start / running signal of the cooling tower so it will run when the tower is running.
For the purging of the collected debris in the filter, there is usually a timer where the frequency and duration of purging to drain can be set.
Skid / base
The filtration system, pump, and control / electrical panel will be supplied mounted to a skid/metal frame.
Who should design and install the sweeper system?
The best way is to get the cooling tower manufacturer to design and install the sweeper system.
This way, it will be specific to the tower, and if there are any problems, there will not be any grey areas or blame between the tower manufacturer and 3rd party supplier.
Easier to keep it all together.
How do you maintain a sweeper system
Maintenance for the system is pretty minimal, as can be seen in the table below, and would be completed in line with the cooling tower maintenance checks:
- Ensure that the system is isolated from the electrical system
- Ensure the pumps are not able to start automatically
|1||Open the control panel and check for any corrosion/water damage.||X|
|2||Check for any loose wiring connections||X|
|3||Check lamps operate on the control panel||X|
|4||Check time setting and duration of purging the system, and is in line with documented requirements.||X|
|5||Check integrity of skid/base that the equipment is mounted to||X|
|6||Remove all dust, oil, dirt, water, chemical from the exterior of the pump.||X|
|7||Ensure the pump air inlet is clear of debris and not obstructed.||X|
|8||Visually inspect the anti-vibration mounts for the pump.||X|
|9||Visually inspect the valves installed on the system for wear and tear.||X|
|10||Operate each valve installed on the system to ensure it can open and close as intended.||X|
|11||Check integrity of all pipework||X|
|12||Check spray nozzles condition||X|
|13||Check the cold water basin of the tower, focusing upon the cleanliness, ensuring the nozzles are working correctly and cleaning the correct areas.||X|
|14||Check pump bearings are greased and lubricated in line with manufacturer requirements; replace bearing if required. [If the pump has been removed, replace gasket]||X|
Troubleshooting sweeper system
Flow rate from Nozzles is not sufficient
If it is found that the flow rate from the nozzles is not sufficient to conduct the following checks / remedial works:
|Ref||Issue||Check / remedial action|
|1||Is the pump operating correctly?||Check flow rate / electrical running currents etc.|
|2||Is the suction pipework fully submerged, not drawing air into the system.||Check pipework is connected, and no air is being drawn in.|
|3||Is the filter clean and debris been purged, allowing water freely to flow through?||Purge the filter and check it is clean.|
|4||Is the purge valve closed whilst nozzles are operating?||Ensure valve is closed.|
|5||Has the pipework been leak-tested to ensure all joints are not passing any water,||If not, complete the low pressure – pressure test.|
|6||Was the pipework flushed through before installing the nozzles||If not, remove all nozzles, clean, and flush through the pipework to ensure no foreign objects.|
Filter / Separator is not purging
If it is found that the filter/separator is not purging, conduct the following checks / remedial works:
|Ref||Issue||Check / remedial action|
|1||Is the pump operating correctly, power and flow rate when the filter is in purge mode||Check flow rate / electrical running currents etc.|
|2||Is the purge rate set correctly, frequency of purge, and duration?||Check inline with manufacturers literature|
|3||Are valves closed in the purge line that should be open?||Check all inline valves to ensure that they are in ‘design’ condition under normal operation.|
|4||Does the purge valve operate, have power, and be able to operate if commanded.||Push the test switch on the control panel/valve to test.|
Separator is always purging
If it is found that the filter/separator is always purging, conduct the following checks / remedial works:
|Ref||Issue||Check / remedial action|
|1||Is the purge valve stuck ‘open’ by debris||Check|
|2||Is the purge rate set correctly, frequency of purge, and duration?||Check inline with manufacturers literature, and is not set to constant.|
Return on Investment
According to Baltimore Aircoil Company, the return on investment for a cooling tower using an existing filtration system is 1.3 years: